How many RPM'S

[Will]

I have a 99 ranger 4X4 with a 3.0 with 410 gears. I run about 3000 rpm's around 60-65. Is that right. Seems a bit high to me. Thanks for your responses in advance.

According to my spreadsheet--with 33s and 4.10s and an auto at 3000rpm you should be going 94mph in OD and 71mph in 3rd.

If your speedo has not been corrected then you should be seeing about 65 on the speedo when you are going 70.

I have to conclude that your overdrive is kaput.

 

[Kdawg532]

i run 235 75r15 and at 65 i am barley hitting 2500 with 4.10s you think my speedo could be off??

 

[Kdawg532]

According to my spreadsheet--with 33s and 4.10s and an auto at 3000rpm you should be going 94mph in OD and 71mph in 3rd.

If your speedo has not been corrected then you should be seeing about 65 on the speedo when you are going 70.

I have to conclude that your overdrive is kaput.

x2 i didnt see this before i posted

 

[mdmarble]

What size tires are on it? (3000 sounds about right if you have 235/75R15s on it).

The 3.0L is most efficient around 2700-3000 RPM (65 MPH). You could maybe put slightly larger tires on it though.

When you say "most efficient," do you mean fuel economy or power? At 50-55 mph I think I'm a tad under 2,000 RPM. When I run up to 70-75 mph I'm close to 2800 RPM. Would any one know if I'm getting better fuel economy going faster?

 

[4x4junkie]

When you say "most efficient," do you mean fuel economy or power?

Fuel economy. Its very close to best power there too though.

As for going faster, you're then battling against aerodynamics, so no, your MPG will not be better.

MPG MIGHT improve a bit at 65 MPH by not using OD if it puts it around 2800 RPM at that speed.


Will's spreadsheet thing has me confused though
I have 33s and 4.10s in my Ranger, and at 3000 RPM it's closer to 80 MPH. The speedo is almost dead-accurate on it, too (maybe 1 MPH fast at 65). The auto's OD isn't THAT much different than the M5OD's, is it?

 

[86ford]

junkie i think elevation effects his chart to some extent. as for the ratio diffrence, the auto is .04 lower numerically than the m5od1. its .79 m50d and .75 for a 94 auto.

86

 

[Will]

I'll attach my spreadsheet. Here is the formula though--very simple.

Tire diameter = 32.8
Circumference = 103.2 (pi * dia.)
O/D = .79
Axle = 4.10
Engine RPM = 3,000

(103.2 / 12) x 3000= 25800 = number of feet per minute with no gearing

.79 x 4.10 = 3.239 = final gearing

Actual feet per minute = fpm no gear / final gear = 7965.42 fpm

Divide fpm by 5280 to get miles per minute

Multiply miles per minute by 60 minutes to get mph.

7965.42 / 5280 = 1.5 miles per minute x 60 minutes is 90 mph

My spreadsheet is based on that but I put in some things like a calculator for shift points and it shows speed per gear and crawl ratio. I made it 10 years ago (so I hope nobody finds a mistake!) in Works and kept changing it over time. I don't know how much everyone knows but you can select, copy and paste the entire group of blocks down the current page to add a vehicle, or just save-as and make a new sheet and change that one.

I make spreadsheets for everything so I only have to think once per topic.

 

[Will]

http://therangerstation.com/tech_library/AutoTrans.html

Those are the ratios for an auto. Just put them in to the blocks indicated. If it's a 3 or 4-speed it doesn't matter. Put a zero in the blocks you don't use if you want.

 

[doubletap4311]

So, How many gear do or should I have with my auto w/ overdrive????

 

[Will]

You have the 4R55E I believe.

 

[4.56-FX4]

Not trying to start an argument, but if you put bigger tires on AND downgear accordingly, your speedo should be close (if not perfect).

I've gone to 4.56's from 4.10's and from 245/75-16's to 33's and my speedo is very close. I measured 1 mile with my odometer and my GPS showed like .99 or 1.01 miles. Close enough for me.

 

[Will]

That's exactly the point of regearing after you put on larger tires.

 

[4.56-FX4]

With 33s at 60-70MPH you are actually going much faster than your speedo says...

That's exactly the point of regearing after you put on larger tires.

Yeah, I was posting in reference to Hahnsb2's post.